21 cm Mörser 10.
In the 1913–14 war plan, the younger Moltke determined that Germany would concentrate the mass of her army – sixty-eight divisions – against France and only nine against Russia (with two reserve divisions watching the North Sea coast against a British landing). Unless the French attacked first, and in strength, in Lorraine, the main German attack would be made through Belgium north of the Meuse. Moltke could not risk having an intact Liège cutting the supply lines of the German 1st and 2nd Armies.
Heereskavalleriekorps 2 (HKK 2 – 2nd Cavalry Corps) would advance with 2 and 4 Kavalleriedivision (KD – Kavalleriedivision – cavalry division) to cross the Meuse north of Liège to take up a position north-east of the fortress and send patrols into Belgium. 9 KD would operate south of Liège.
To take Liège quickly, six brigades, that had not had time to mobilise and were still at peacetime strength (about 25,000 infantry, 124 field artillery pieces and four 21cm mortars) would conduct a quick attack on the night of the fourth to fifth mobilisation days in order to pass between the individual forts, before the Belgians had time to prepare field fortifications between them. The routes had been reconnoitred and established by German General Staff officers in peacetime, who were to act as guides in wartime. In almost all cases the routes followed a major road; little or no attempt was made to infiltrate cross-country. They would seize the city – which was not protected by a wall – and the individual forts would presumably see the futility of further resistance and surrender.
‘Presumably’ because the only notes that still exist concerning the coup de main against Liège are in 1913–14 German deployment orders (1913–14 Aufmarschweisungen), which do not state why or how, if the forts did not surrender outright, that five brigades of infantry (six in 1914), supported by four 21cm mortars, were going to take twelve forts.
The only logical explanation is that Moltke was assuming that Liège would be completely unprepared to defend itself. Moltke apparently expected that in addition to the garrison of the forts, the Belgians would have the peacetime garrison of 6,000 men and 3,000 Garde Civique. Not only would there be no Belgian forces in the intervals between the forts, allowing the German brigades unopposed passage into the city proper, but that the forts too would be unready: best case, still in peacetime caretaker status, worst case without their complete garrison and store of munitions and supplies. Under such circumstances, one or two forts might be overrun or surrender and the rest of the forts would recognise the futility of further resistance. Moreover, it was no state secret that the Belgian 3 DA HQ was at Liège. The German attack had to be made before 3 DA was combat-ready.
The General Staff brochure, Liège-Namur, written in 1918, says that Ludendorff was responsible for ‘the concept and preparation of the attack’. Ludendorff says that the coup de main against Liège was his idea, with the caveat that, once inside the central city and in possession of the citadel it would be possible to easily reduce the individual forts. Ludendorff said that in 1914 he was assigned to the 2nd Army, which had the responsibility of conducting the operation, because of his knowledge of the Liège attack, which was otherwise a closely guarded General Staff secret.
In fact it seems likely that Ludendorff, who had no particular expertise in fortress warfare and was the chief of the Aufmarschabteilung (deployment section) of the General Staff, had no more responsibility for planning the attack than preparing the rail-march tables. Kabisch says that the detailed plan for conducting the attack was written by Brigadier General Schwarte and Section 4 (Western Fortresses) of the great General Staff. The plan was first developed in the 1908–09 Aufmarsch (deployment plan).
If the first attack failed, it would be repeated on the tenth day of mobilisation. If Liège had not fallen by the twelfth day of mobilisation, it would be necessary to transit Dutch territory at Maastricht.
The Liège Myth
Any history of the Battle of Liège attributes the fall of the fortress almost exclusively to the effect of the super-heavy German 42cm guns, an explanation that the Germans fostered themselves, since it emphasised the effectiveness of a German ‘wonder weapon,’ which would presumably demoralise the enemy. This is clearly the intent of the German official history Der Weltkrieg I, which emphasises the 42cm to the exclusion of the rest of the German siege artillery. The Belgians, Moranville in the lead, attributed the fall of Liège entirely to the German super-heavy artillery, which excused the rapid surrender of the Belgian forts. These monster guns continue to fascinate historians of the Marne campaign and their readers.
Barbara Tuchman’s Pulitzer Prize-winning The Guns of August combines ‘common knowledge’ with dramatic prose and is therefore the most popular book on the Marne campaign. She gives her imagination free rein: for example, according to Tuchman the Austrian Skoda 30.5cm mortars were employed at Liège (they weren’t), and the destruction of Liège was caused solely by super-heavy artillery; the German 21cm mortars are not mentioned.
John Keegan’s The First World War, an exceptionally popular and influential military history, repeats the Liège ‘common knowledge’ verbatim: according to Keegan, the destruction of the Liège forts was due solely to the German 42cm guns. Keegan dutifully footnotes his sole source concerning Liège, Christopher Duffy’s ‘The Liège Forts’ in Purnell’s History of the First World War, I, 131–8. This is a useful demonstration of how ‘common knowledge’ becomes entrenched. Purnell’s was a populist weekly magazine, first published in 1970, which had 128 issues. Each magazine was about thirty pages long and covered perhaps four different topics. Each article was heavily illustrated with drawings and photos: Duffy’s had four fully illustrated pages, two half-illustrated and only two of text. Duffy cited eight sources, only two of which had specific information about the siege of Liège. This is not a well-researched article, which would explain why the 21cm are mentioned once. For good measure, Duffy throws in the participation of the Austrian 30.5cm, which never fired at Liège. The strongest part of the article are drawings of the 30.5cm and 42cm. But the 42cm get credit for everything.
In fact, nine of the twelve Liège forts were destroyed by just thirty-two German 21cm mortars, exactly the gun calibre that Liège was designed to defeat. Only one fort, Loncin, fell to the 42cm gun fire – Pontisse had been wrecked by 21cm fire before the 42cm arrived – and even here the 42cm fire was supplemented by the fire of other weapons. The last two forts surrendered, one while under a short period of 21cm fire, the other while not under fire at all.
And Liège fell with dizzying speed. Fort Barchon was reduced on 8 August by the fire of six 21cm mortars, d’Evegnée on 11 August by four 21cm mortars in two days of bombardment. The mass of the siege artillery, almost exclusively 21cm mortars, arrived on 12 August. Three forts fell on 13 August, two on 14 August, three on 15 August and the remaining two on the morning of 16 August. The German siege artillery, and principally the four battalions (thirty-two guns total) of the hard-hitting, mobile 21cm mortar of FAR 4 and 9, had reduced Liège in less than four days.
Development of German Siege Artillery
Armies fight the way they have trained to fight. Behind the brilliant successes of the German heavy artillery at Liège, then Namur, Maubeuge and Antwerp, lay nearly twenty years’ worth of work in developing doctrine, equipment, and good, hard training, especially the live-fire shoots at the artillery MTA and the fortress General Staff exercises. Lombard reported that from the very start German artillery fire was ‘devastatingly accurate’.
By 1883 the German siege artillery faced the daunting prospect of massive French fortifications from Verdun to Belfort, and Antwerp, which led the Chief of the General Staff, Schlieffen, and the General Inspector of the Artillery, to develop the ‘Heavy Artillery of the Field Army’ (schwere Artillerie des Feldheeres), which would consist of a battalion of 15cm guns at the corps level and 21cm guns at the army level.
In 1902 the corps batteries began to receive the new 15cm schwere Feldhaubitze 02 (sFH 02). This was a revolutionary new design, with a recoil brake which kept the gun stable in position and allowed a far more accurate and higher rate of fire. The steel gun tube reduced weight and increased mobility. Maximum effective range went from 6,000m to 7,400m. A battery consisted of four guns and two munitions wagons, a battalion of four batteries and a light munitions column. The mission of the howitzers was to provide corps general support artillery, conducting counter-battery fire against field artillery equipped with armoured shields, and against dug-in infantry. It was not a siege weapon.
The German 21cm mortar in the 1890s was ‘extremely unwieldy’. In 1909 the army-level artillery received the new 21cm mortar, which also had a recoil brake, an armoured gun shield, weighed about 9000kg and fired a 100kg shell 9,400m. It was broken down to three pieces for movement. A particular innovation was the Radgürtel: a wheel with flexible rectangular wooden plates affixed. One plate was always in contact with the ground, and significantly reduced the ground pressure generated by firing the weapon, and therefore no longer required a special base plate. A battery included six OFF, thirty-five NCOs, 218 EM and 150 horses. Each mortar battalion had two batteries, each with four guns, and a light munitions column. The mission of the 21cm mortars was to engage French border fortifications, especially the Sperrforts located between the four main fortresses. There was also a 13cm flat-trajectory gun with a range of 15km, which in siege operations would allow rear-area lines of communications to be engaged in depth.
For a considerable period the largest German siege weapon was an older-type 30.5cm mortar which had been introduced in 1893. It had a maximum effective range of 7km and a shell weighing 400kg. Its official designation was a ‘heavy coastal mortar’ and its code name was ‘β-Gerät’ – ‘β apparatus’. Initially it was moved on narrow-gauge field railways, later on tractor-pulled trailers. Only nine were purchased. It was followed in 1909 by ‘β-Gerät 09’, which was also pulled by tractors and trailers. Only two of these were acquired.
In 1909 the heavy artillery also acquired a 42cm ‘short naval mortar’ (kurze Marinekanone) with a range of 14km and a 930kg shell. Its code name was γ-Gerät. It needed to be moved by regular rail line into the firing position. Firing tests showed that the weapon had outstanding accuracy as well as a very effective shell, so that in 1913–14 four more were delivered. The disadvantage of the mortar was its great weight and consequent dependence on rail mobility.
The success of the Radgürtel for the 21cm mortar led the artillery commission to use it for heavier weapons. To test this, in 1910 Krupp developed a 28cm howitzer on a wheeled Radgürtel chassis, in 1911 a 30.5cm howitzer.
In 1914 the German field army had 408 15cm howitzers, 112 21cm mortars, sixteen 10cm guns, one 28cm howitzer on a wheeled carriage, twelve 30cm mortars and seven 42cm mortars. The reserve foot artillery units included 400 15cm howitzers, 176 10cm guns and thirty-two 13cm guns. There were 420 pieces of heavy artillery without horse teams and 834 pieces of heavy fortress artillery.